Ducts are extensively utilized in heating, cooling and ventilating systems to distribute heated or cooled air throughout a structure. These ducts are commonly formed from differing gauges of sheet metal in sections of predetermined lengths which are then connected to one another to form a continuous duct system for distributing air.
It is oftentimes necessary to connect two sections of duct utilizing a corner duct section to accommodate changes in the direction of the duct. These corner sections may exhibit a 90°, 45°, 30° or any other change in direction.
It is known in the art that when cylindrical ducts having circular cross-sections are utilized, an elbow rotator apparatus may be employed to rotate the differing sections of a formed, cylindrical duct so as to define the appropriate corner duct section. One example of such an elbow rotator is disclosed in commonly assigned and pending U.S. patent application Ser. No. 10/744,279, entitled ELBOW ROTATOR and filed on Dec. 23, 2003, herein incorporated by reference in its entirety.
Although elbow rotators for cylindrical duct section are known, these apparatuses are only employed after a straight, cylindrical duct workpiece is cut and formed. Elbow forming apparatuses are also known in the art to accomplish the cutting and formation a straight, cylindrical duct workpiece, however the known elbow forming apparatuses suffer from certain drawbacks.
In particular, known elbow formation apparatuses are capable of holding a straight, cylindrical duct workpiece so that a series of cuts may be made in the workpiece to define thereby the sections of the workpiece that may be subsequently rotated to form a corner duct section. A series of beads may also be formed in the workpiece, in the area of each cut, so that adjacent sections of the corner duct nest within one another, thus providing a formed joint capable of permitting rotation about the center, longitudinal axis of the workpiece.
Known elbow formation apparatuses, however, first cut the cylindrical duct workpiece, and then impart a bead to the recently separated section of the workpiece to facilitate the nested mating of the two sections. In performing the cutting operation first, that is, performing the first cut prior to the formation of a bead, known elbow formation apparatuses suffer from the shaving of slivers of metal caused by the falling of the top cylindrical duct section into the path of the cutting die of the elbow formation apparatuses. Such problems are exasperated when the cylindrical duct workpiece is formed from thin gauge metal.
With the forgoing problems and concerns in mind, it is the general object of the present invention to provide a pre-beading apparatus for use with metal duct workpieces which avoids the formation of metal slivers, and promotes the more efficient manufacture of elbow duct sections.